From fe5010380a3a18ca85f39403e8032de1dddbe905 Mon Sep 17 00:00:00 2001 From: Sage Weil Date: Thu, 22 Aug 2013 15:54:48 -0700 Subject: [PATCH] mon/Paxos: fix another uncommitted value corner case It is possible that we begin the paxos recovery with an uncommitted value for, say, commit 100. During last/collect we discover 100 has been committed already. But also, another node provides an uncommitted value for 101 with the same pn. Currently, we refuse to learn it, because the pn is not strictly > than our current uncommitted pn... even though it is the next last_committed+1 value that we need. There are two possible fixes here: - make this a >= as we can accept newer values from the same pn. - discard our uncommitted value metadata when we commit the value. Let's do both! Fixes: #6090 Signed-off-by: Sage Weil --- src/mon/Paxos.cc | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/src/mon/Paxos.cc b/src/mon/Paxos.cc index 347810775c0..fa3e2089842 100644 --- a/src/mon/Paxos.cc +++ b/src/mon/Paxos.cc @@ -328,6 +328,15 @@ bool Paxos::store_state(MMonPaxos *m) // apply. decode_append_transaction(t, it->second); } + + // discard obsolete uncommitted value? + if (uncommitted_v && uncommitted_v <= last_committed) { + dout(10) << " forgetting obsolete uncommitted value " << uncommitted_v + << " pn " << uncommitted_pn << dendl; + uncommitted_v = 0; + uncommitted_pn = 0; + uncommitted_value.clear(); + } } if (!t.empty()) { dout(30) << __func__ << " transaction dump:\n"; @@ -425,7 +434,7 @@ void Paxos::handle_last(MMonPaxos *last) // did this person send back an accepted but uncommitted value? if (last->uncommitted_pn) { - if (last->uncommitted_pn > uncommitted_pn && + if (last->uncommitted_pn >= uncommitted_pn && last->last_committed >= last_committed && last->last_committed + 1 >= uncommitted_v) { uncommitted_v = last->last_committed+1;